Exposure should be
graded
repeated and regular
prolonged
This is my experience with exposure therapy
You list all the things that make you anxious from least anxious to most anxious. And you start at the bottom of the list.
For example looking at a picture of a spider, then graduate to watching a video of a spider, then going into a room with a spider, and finally having a spider in your hand.
If you expose yourself to the room full of spiders first failure is almost certain.
While exposed to anxiety it reaches a peak and then falls away. So prolonged means staying with the anxiety until it peaks, each time the peak isn't as intense and it falls away more quickly.
It has worked for me. I gave a talk at a workshop with a Fabio wig and a fluffy shark, people cheered and applauded at the end.